IN CONCERT 1964 is heaven for old-school folkies. The double album was recorded live in the innocent days before Dylan went electric and features Peter, Paul and Mary performing most of their big hits. "Blowin' in the Wind," "The Times They are a Changin'," "Puff the Magic Dragon," and "500 Miles" appear in versions largely indistinguishable from the original studio renditions. Paul Stookey had done time as a stand-up comedian before the group got together, and the concert features a fair amount of between-song comic shtick that has retained its humorous bite as it has aged.